When is the right time to introduce your child to the person you're dating?

If you're a single parent, how soon do you introduce your child to the person you're dating?

It has been a big concern, especially when you open the door and unwittingly allow a monster in your home with your child. We've seen case after case, such as Maleah Davis, where the mother says her boyfriend killed her daughter and buried the girl's remains in Arkansas.

But do single parents see the warning signs or the writing on the wall? How do you know when to trust a person with your child?